PS-9378: Backport PS-9302 (WRITESET perf improvements) to 8.0 (8.0)

[percona-ysorokin]

https://perconadev.atlassian.net/browse/PS-9378

This patch was originally created for the 8.4 branch where the only
available binlog transaction dependency tracking mode is 'WRITESET'.
However, it also makes sense to backport this to 8.0 as the same
code paths are used when user explicitly set the
'binlog_transaction_dependency_tracking' system variable to 'WRITESET'
(by default in 8.0 series, this variable is set to 'COMMIT_ORDER').

Cherry-picked PS-9302
"Improve performance for binlog_transaction_dependency_tracking=WRITESET"
(https://perconadev.atlassian.net/browse/PS-9302) from 8.4.

Problem:
Comparing to 8.0 where the default value of
binlog_transaction_dependency_tracking was COMMIT_ORDER, 8.4 introduces a visible write performance drop.

Cause:
8.4 uses WRITESET dependency tracking. For this tracking we maintain a map of binlog_transaction_dependency_history_size for row_id to newest transaction sequence_number which modified a given row. Every new transaction needs to check its dependency by examining the map (find), which is done with logarithmic complexity.

Solution:
Change std::map to std::unordered_map. This allows us to find a row dependency in constant on average complexity.

[dlenev]

Hello Yura!

I think it is worth mentioning in commit comment that even though in 8.0 WRITESET dependency tracking is not default, it still makes sense to backport the patch from 8.4,
as many people might be using this non default dependency tracking and the patch is really straightforward.

Otherwise, LGTM.

[dlenev]

You might want to fix typos in commit message like:

backpot -> backport
Cherry-piked -> Cherry-picked

Otherwise LGTM.